1. Field of the Invention
The present invention relates to an absorber with a hole in a cryogenic particle detector, particularly a metallic magnetic cryogenic detector. It is to align the metallic magnetic temperature sensor relative to a pick-up loop of a measuring means. A small hole makes it possible to estimate the position of the temperature sensor on one side of the absorber from the other side. The hole is made with a high power pulse laser.
2. Background of the Related Art
A metallic magnetic cryogenic detector is one of the low temperature detectors which have demonstrated their high energy resolution. Like other low temperature detectors, it has an absorber to absorb energy of incident particles, such as x-rays, gamma rays, electrons and other particles. It also has a temperature sensor whose physical property varies with temperature. The mechanical and thermal connection between the absorber and the temperature sensor are typically made with an ultrasonic wedge-bonder. The temperature sensor is made of a material, whose magnetization keeps its paramagnetic property even at very low temperatures below 100 mK. The change of the magnetization due to the absorption of the incident energy is magnetically measured with a pick-up loop wound around the temperature sensor. The measuring means can be a superconducting quantum interference device (SQUID) or a superconducting planar coil connected to another SQUID.
When energy of a particle to be detected is absorbed in the absorber of the metallic magnetic cryogenic detector, the temperature of the absorber varies according to the deposited energy. The SQUID measures a magnetic flux variation caused by the temperature variation to obtain the deposited energy.
In order to precisely measure a temperature variation, it is required to locate the temperature sensor inside a pick-up coil of the SQUID. In the process of attaching the temperature sensor to the absorber having a thickness of 1 through 5 μm, a pressed mark is formed on the backside of the absorber. The pressed mark is used for aligning the temperature sensor relative to the pick-up loop coil. However, the pressed mark is not often distinct. Thus, it requires an extreme caution for accuracy when aligning the temperature sensor relative to the pick-up coil because of the limited estimation of the sensor position.
Furthermore, when a absorber thicker than 10 μm is used, the pressed mark is barely noticeable. It makes it difficult to align the temperature sensor with the pick-up loop coil.